Pneumatic springs, commonly referred to as air springs, have been used for motor vehicles for a number of years to provide cushioning between movable parts of the vehicle, primarily to absorb shock loads impressed on the vehicle axles by the wheels striking an object in the road or falling into a depression. The air spring usually consists of a flexible rubber sleeve or bellows containing a supply of compressed fluid and has one or more pistons located within the flexible resilient sleeve. The piston causes compression and expansion of the fluid within the sleeve as the sleeve compresses and expands as the vehicle experiences the road shocks. The spring sleeve is formed of a flexible elastomeric material which permits the pistons to move axially with respect to the sleeve and within the interior of the sleeve.
The ends of the sleeves are sealingly connected to the piston and/or an opposite end cap if only one piston is used in the particular spring construction. The clamping of the ends of the flexible sleeve onto the piston and/or end member is always one of the important and major assembling steps in the production of air springs. Heretofore, the usual manner of sealing the sleeve against the piston and/or end cap has been by clamping an exteriorly located metal band against the flexible sleeve which crimps and squeezes the rubber material thereof against a sealing surface of the piston or end member. These prior art sealing methods and structures require a permanent deformation of the clamping band and require equipment to supply sufficient pressure to the metal clamping band to permanently deform the metal upon crimping it radially inwardly against the sealing surface of the adjacent air spring member.
It is preferred for certain air spring applications to internally clamp one or both ends of the flexible sleeve outwardly against an inner surface of the end cap and/or piston member to save space and reduce the number of components needed in the air spring assembly. Several known prior art devices having flexible sleeves including air springs use an internal clamping band and are shown in the patents described briefly below.
U.S. Pat. No. 2,115,072 shows the sealing of both ends of the sleeve of an air spring by trapping them in an annular groove of end caps in combination with external annular clamping rings which are bolted to the end caps.
U.S. Pat. No. 2,641,486 shows a usual split ring clamping arrangement. The split ring is compressed by reducing the spacing of the gap between the split ends of the ring afterwhich the ring expands outwardly against a sleeve of material clamping the sleeve internally against an outer supporting structure. However, split rings cannot readily obtain the amount of clamping force required to form a satisfactory seal in an air spring application.
U.S. Pat. No. 3,027,176 shows an air spring having an internal sealing arrangement by use of an annular bead at the ends of the flexible sleeve similar to the sealing bead of a pneumatic tire.
U.S. Pat. No. 3,053,528 shows an air spring in which one end of the flexible sleeve is internally clamped against an outer cylindrical housing by a wedge-shaped end cap. The cap is forced into a wedging relationship with the end of the flexible sleeve by the internal fluid pressure of the air spring.
U.S. Pat. No. 3,527,451 shows another shock absorber which has an internal band which clamps the flexible sleeve against the inner surface of an outer cylindrical housing. It is believed that the internal clamping is achieved either by a wedging action of the internal clamping band against the trapped flexible sleeve end or by a permanent deformation of the internal clamping band in a similar manner as the crimping of a sealing band on the exterior of the flexible sleeve as used in many prior external clamping band arrangements.
U.S. Pat. No. 4,489,474 discloses an air spring in which the flexible sleeve is clamped by external sealing bands to the end cap members.
U.S. Pat. No. 4,506,910 discloses an air spring having a flexible sleeve clamped to an inside of an open end of an end cap.
U.K. Patent No. 2,116,667 discloses an air spring structure containing a flexible sleeve with one edge rolled over a metal ring which is compressed in a fluid tight manner against the inside of a cylinder by a ring in which the end cap is formed of a plastic.
U.S. Pat. No. 4,037,305 discloses a cylindrical core and a sealing ring inserted into an outer casing resulting in a fluid tight seal and limited outward expansion of the side wall of the outer casing. The outward diameter of the inner cylinder is generally equal to the inner diameter of the casing.
U.S. Pat. No. 4,489,830 discloses a retaining device wherein the sidewalls expand at insertion of a second member and then contract slightly to grasp the member as it settles into grooves formed in the side wall.
U.S. Pat. No. 4,653,170 discloses a device where an inner cylinder and a sealing means is inserted into a friction fit with an outer casing where the side walls of the casing are elastically expanded outwardly by the insertion.
German Patent No. 1,273,939 discloses a sealing ring inserting tool.
U.S. Pat. No. 3,140,085 discloses an air spring structure containing a sleeve in which one edge is rolled over a metal ring which applies a squeezing action to the rolled edge of the flexible sleeve or diaphragm as it is sidably received within the interior of a shock absorbing cylinder. The ring has a cylindrical configuration and the diaphragm is maintained in position between a supply of oil and a supply of gas trapped within the shock absorber cylinder.
Therefore, the need has existed for an improved air spring and method of making the same which contains an internal sealing band for sealingly securing the flexible sleeve against an end cap and/or piston member of the air spring.